During the course of a study on pipeline coatings, the Applicant was concerned with polymer compositions. Following this work, compositions of particular interest for coating pipelines, particularly externally, were developed, these compositions containing at least one heat stable thermoplastic polymer which is amorphous or of low crystallinity, and at least one modified epoxy resin.
The present invention concerns polymer compositions, and a process for synthesising these compositions. It also concerns the use of these compositions, in particular for coating conduits, especially pipeline coatings, to obtain pre-impregnates for the production of composition materials, also to produce adhesives and mastics, in particular to rehabilitate oil or geothermal wells or more generally any excavations.
Pipelines are metal tubes, often formed from steel, essentially used in wells to transport crude oil and natural gas, but any type of fluid could be transported by this pipeline. The internal surface of the pipeline is corroded by the transported fluid. When the transported fluid is oil, the sulphur-containing compounds contained in the oil are the main causes of the corrosion. When drilling offshore, the external surface of the pipeline is also corroded by sea water. Treating conduit surfaces has already been described in the prior art. As an example, United States patent U.S. Pat. No. 5,447,798 describes a concrete conduit on which an intermediate layer is deposited which is a mixture of epoxy resin modified by a polysulphide and concrete, then a layer of epoxy resin modified by a polysulphide.
The principal problem with depositing a polymer on a metal surface, for example the external and/or internal surface of a pipeline, for example of steel, is the behaviour of the polymer when it is subjected to heat stress. Even if the oil is cooled before transporting it, the pipeline is often heated to a temperature of about 50xc2x0 C. to 200xc2x0 C. by contact with hot oil. Certain polymers, for example polypropylene, tend to deform and no longer adhere to the metal once the temperature exceeds 130xc2x0 C. Other polymers, such as polyetherimides or polysulphones, adhere at high temperatures but their application temperature (at which it is deposited on the metal) is higher, about 360xc2x0 C. Further, metals, in particular steel, may undergo phase distortions from a temperature of about 250xc2x0 C., and certain of their mechanical and physical properties can be altered.
In addition, good adhesion of the polymer at a higher temperature enables the oil to be transported without the need to cool it, or at least it only needs to be cooled to a lesser extent. At a relatively high temperature, oil is less viscous and therefore easier to transport.
The criteria which the desired polymer compositions must satisfy are thus a temperature for deposition on steel such that the steel is not altered and good adhesion to the steel.
The present invention provides a polymer composition which overcomes the above disadvantages. The application temperature at which the polymer composition of the present invention is deposited onto steel is about 180xc2x0 C. to 250xc2x0 C., and in that temperature range, the mechanical behaviour of steel is good. The polymer composition of the present invention has particular good adhesion, in particular to steel, high stiffness, and good resistance to sea water. Further, these qualities are not substantially altered when the compositions are aged.
The polymer compositions of the present invention contain at least one heat stable thermoplastic polymer, preferably amorphous, and at least one epoxy resin modified by at least one aromatic polyamine, preferably sterically hindered. The heat stable thermoplastic polymer preferably represents about 15% to 98%, more preferably 35% to 80% by weight, with respect to the total composition weight; preferably, the modified epoxy resin represents about 2% to 85%, more preferably about 20% to 65% by weight, with respect to the total composition weight.
In the present description, the xe2x80x9caromatic polyaminexe2x80x9d contains at least two primary amine groups in its molecule. It is preferably sterically hindered, i.e., it contains at least one alkyl substituent containing 1 to 12 carbon atoms located alpha to one of the amine groups.
The most frequently used thermoplastic polymers are polysulphones and polyetherimides.
The term xe2x80x9cpolysulphonexe2x80x9d may be the source of an ambiguity. The first polymer of commercial importance with a base unit containing a sulphone groupxe2x80x94SO2xe2x80x94 was the polymer sold by AMOCO under the trade name UDEL. Because of this, this particular polysulphone is often designated by the generic term polysulphone. In the present description, the term xe2x80x9cpolysulphonexe2x80x9d is used in its generic sense, and not just the limiting sense of a UDEL type polysulphone.
The polysulphones used in the polymer compositions of the invention are preferably aromatic polysulphones and, more preferably, UDEL type polysulphones, RADEL A polysulphone type polyether-sulphones sold by AMOCO, and RADEL R type polyphenylene sulphones also sold by AMOCO.
The polyetherimides used in the polymer compositions of the invention are preferably ULTEM type polyetherimides sold by General Electric Plastics.
These polyetherimides can be used alone, mixed with each other or mixed with other polymers such as polyphenylene ethers, aromatic polyetherketones or polyphenylene sulphides. Polymer compositions of the present invention comprising polyphenylene ethers contain about 5% to 98% by weight thereof with respect to the total weight of the thermoplastic polymers. Polymer compositions of the present invention comprising aromatic polyetherketones contain about 1% to 50% by weight thereof with respect to the total weight of thermoplastic polymers. Polymer compositions of the present invention comprising polyphenylene sulphides contain about 1% to 50% by weight thereof with respect to the total weight of thermoplastic polymers.
The epoxy resins modified by at least one aromatic polyamine, preferably sterically hindered, used in the polymer compositions of the present invention are epoxy resins formed from at least one polyepoxide containing at least two epoxy groups in its molecule and at least one aromatic polyamine, preferably sterically hindered, the mole ratio of the amine to the epoxy being such that each amine group corresponds to 1.6 to 2.6 epoxy groups.
Preferred aromatic polyamines are selected for their low reactivity and for their non toxic nature.
The epoxy resin can be selected from the group formed by the following commercially available resins: the diglycidylether of bis-phenol-A or bis-phenol F, bis-phenol formol epoxy resin, phenol-novolac epoxy resin, cycloaliphatic epoxy resins, tri- or tetrafunctional epoxy resins, resins formed from triglycidylether-isocyanurate and/or triglycidylether-cyanurate and/or triglycidyl-cyanurate and/or triglycidyl-isocyanurate or mixtures of at least two of these epoxy resins.
The epoxy resins obtained from the epoxy resins cited in U.S. Pat. No. 4,921,047 can also be used in the present invention.
The aromatic polyamines used in the polymer compositions of the present invention includes a first series of aromatic amines comprising a single aromatic ring such as 3,5-diethyl-2,4-aminotoluene, 3,5-diethyl-2,6-diaminotoluene and mixtures of these two isomers. Usually, a mixture of these two isomers generally known as DETDA is used.
In the second series of amines used in the present invention, amines containing at least two aromatic rings can be considered, these two aromatic rings generally being connected to each other by a bivalent linear or branched hydrocarbon residue containing 1 to 18 carbon atoms. These two aromatic rings are either connected via a bivalent alkylene group or are connected one to the other via a bivalent linear or branched hydrocarbon residue containing 6 to 18 carbon atoms and containing an aromatic ring.
The aromatic polyamine can also contain at least one substituent selected from the group formed by fluorine, iodine, bromine and chlorine. It preferably contains at least two alkyl substituents, each being alpha either side of an amino group.
When the two aromatic rings are connected via a bivalent alkylene residue, this residue is preferably a methylidene group which is non substituted or substituted by at least one radical selected from alkyl radicals and halogenoalkyl radicals containing 1 to 3 carbon atoms. As an example, this alkylene residue is selected from the group formed by the methylidene group, the isopropylidene group, the halogenoisopropylidene groups, and the hexafluoroisopropylidene group. In this case, the amine is preferably selected from the group formed by:
4,4xe2x80x2-methylene-bis(2,6-dimethylaniline) or M-DMA;
4,4xe2x80x2-methylene-bis(2-isopropyl-6-methyl-aniline) or M-MIPA;
4,4xe2x80x2-methylene-bis(2,6-diethylaniline) or M-DEA;
4,4xe2x80x2-methylene-bis(2,6-diisopropylaniline) or M-DIPA; and
4,4xe2x80x2-methylene-bis(3-chloro-2,6-diethylaniline) or M-CDEA.
Of these amines, 4,4xe2x80x2-methylene-bis(2,6-diethylaniline) and 4,4xe2x80x2-methylene-bis(3-chloro-2,6-diethylaniline) are of particular interest.
When the amine contains two aromatic rings which are connected to each other via a bivalent hydrocarbon residue which may or may not be substituted, containing 6 to 18 carbon atoms and containing an aromatic ring, it is preferably selected from the group formed by:
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-3-chloro-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-3-chloroaniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-3-chloro-aniline);
4,4xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethyl-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dimethyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diethy-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-dipropyl-3-chloro-aniline);
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-disopropyl-aniline); and
3,3xe2x80x2-(phenylene-diisopropyl)-bis(2,6-diisopropyl-3-chloro-aniline).
The polymer compositions of the present invention can also contain catalysts which are active for the reaction between the epoxy resins and the sterically hindered aromatic polyamines. The most frequently used active catalysts are imidazoles, tertiary amines and boron trifluoride based complexes. Additives selected from the group formed by antioxidants, pigments, adhesion promoters, heat stabilisers and organic, mineral or metallic fillers can also be added.
The present invention also concerns the synthesis of polymer compositions containing at least one thermoplastic polymer, preferably amorphous, and at least one epoxy resin modified by at least one aromatic polyamine.
Synthesis is generally carried out without a solvent in the molten state at a temperature of about 100xc2x0 C. to 250xc2x0 C., preferably about 150xc2x0 C. to 200xc2x0 C. by bringing the reactants into contact in suitable proportions to obtain a final composition which preferably has a thermoplastic polymer content of about 15% to 98% by weight, more preferably about 35% to 80% by weight, and a modified epoxy resin content of about 2% to 85% by weight, more preferably about 20% to 65% by weight, with respect to the total composition weight.
The synthesis of the present invention can be carried out using any type of mixer: preferably, a twin screw extruder is used.
The epoxy resins, aromatic polyamines and any additives can be introduced into the mixer in the form of a premix to which the thermoplastic polymer is added. It is also possible to introduce each reactant into the reactor separately via different inlet zones or via a single inlet zone. The scope of the invention also encompasses forming an initial mixture of thermoplastic polymers and epoxy resins then adding the hardening agent which is the aromatic polyamine. It is also possible to introduce the polyamine into the mixer in a zone close to the zone for recovering the polymer composition.
Once mixed, the polymer composition is formed then it is preferably cured. Curing generally consists of heating the composition to a temperature of about 200xc2x0 C. to 250xc2x0 C., for example for a period of about 10 minutes to 12 hours. This is preferably carried out in an oven.
The properties of the compositions of the present invention, in particular their adhesion properties, are of the order of those required for the most demanding use, in particular for use in the aeronautical industry.
Further, the resistance of these compositions to sea water is good and measurements carried out on compositions which have undergone accelerated ageing show that these compositions were only very slightly altered by that ageing.
These compositions have applications in the fields of surface coatings, in particular for conduits and more particularly for coating pipelines or in matrices of composition materials. They can also be used to produce adhesives and mastics, in particular for adhesives for pipeline junctions and to rehabilitate oil or geothermal wells or, more generally, all excavations.
The following examples illustrate the invention without limiting its scope.
The polymer compositions in the following examples were prepared using a twin screw extruder from CLEXTRAL; this extruder comprised a plurality of positions for introducing the reactants to be mixed.
For these examples, the epoxy resin and aromatic polyamine were first mixed; this mixture will hereinafter be termed the xe2x80x9cpremixxe2x80x9d. The thermoplastic polymers were introduced via an inlet zone and the premix was introduced via a further inlet zone. The rate for the premix was constant, and was introduced using a gear pump. In contrast, the thermoplastic polymers were introduced using a gravimetric metering hopper which enabled the rate of the thermoplastic polymers to be varied, and thus polymer compositions with different modified resin/thermoplastic polymer ratios could be produced.
The thermoplastic polymers were introduced into the extruder""s inlet zone at the end opposite to the zone for recovering the polymer composition. The temperature in this inlet zone was 100xc2x0 C. They were then entrained in a second zone where the temperature was 150xc2x0 C. and into which the premix was introduced. These reactants were then entrained by the twin screw extruder, with the temperature inside the extruder slowly increasing to attain 185xc2x0 C. and the extruder outlet.